中文摘要：

针对非稳态流场中流体测量时存在的问题,在超声波流量计过零点检测判定渡越时间的基础上,采用电压调幅的方法产生超声波换能器激励信号,然后通过检测接收信号的幅值变化特征点定位波形.针对流场中流速不稳定可能导致的波形不稳定情况,采用中值滤波的方法减小误差.为避免ADC芯片位数和AD转换速率限制导致渡越时间测量误差问题,在数字波形特征点判定基础上,采用过零点检测从模拟波形上获得渡越数据.实验结果表明,该方法具有一定的可行性,可以达到对超声波脉冲序列准确处理、定位的目的,测量误差可以控制在在1.5％以内,可以达到二级精度仪表的要求水平.

英文摘要：

Aiming at the matter of fluid measurement in the unstable flow field,amplitude modulation was used to generate excitation signals of ultrasonic sensors,then the amplitude changed feature points of received signals was detected to locate the waveform,based on the transit time determined by zero-crossing detection of ultrasonic flowmeter.Aiming at the unstable waveform caused by the unstable flow velocity in the flow field,median filtering method was used to eliminate caused errors.In order to avoid the transit time measurement error caused by the restriction of the ADC digits and conversion rate,the transit data was collected from analog waveform by zero-crossing detection,based on the feature points determination of the digital waveform.The results indicate that this measure is certain feasible,could process and locate the ultrasonic pulse sequence accurately,the measurement error could be controlled below 1.5％,it can achieve the requirement of the secondary standard of precision.